Morphology, chemical composition, and electrochemical characteristics of colored titanium passive layers

Par Conseil national de recherches du Canada

DOI	Trouver le DOI : https://doi.org/10.1021/la001694s
Auteur	Rechercher : Hrapovic, S.; Rechercher : Luan, B.L.; Rechercher : D'Amours, M.; Rechercher : Vatankhah, G.; Rechercher : Jerkiewicz, G.
Format	Texte, Article
Résumé	Brightly and uniformly colored passive layers on Ti are formed by application of ac polarization in aqueous NH4BF4. A wide spectrum of well-defined colors is accomplished by varying the ac voltage. The passive films are stable in the ambient and in aqueous chloride, perchlorate, and sulfate solutions. Optical microscopy and scanning electron microscopy analyses indicate that the passive layers are compact and do not show fractures or cracks. An X-ray photoelectron spectroscopy (XPS) characterization of the colored passive layers demonstrates that their surface-chemical composition depends on the ac polarization voltage. The main constituents of the passive layers are Tiz+, O2-, and F- (z varies from 4 to 2 depending on the film's depth). Fluoride in the film originates from decomposition of NH4BF4, and it accumulates at the inner metal/passive-film interface. XPS depth profiling shows that the higher the ac voltage applied, the thicker the passive film formed. Electrochemical properties of the colored Ti passive layers are determined by recording polarization curves in the −0.8 to 3.2 V range as well as Tafel plots in the hydrogen evolution reaction (HER) region in 1.0 M aqueous H2SO4. The polarization curves show that the corrosion potential of the colored passive layers shifts toward less-negative potentials indicating that they are more stable than Ti under the same conditions. The passive region for the colored layers resembles that for Ti. The Tafel plots for the HER demonstrate that the passive layers have higher activity toward the HER than Ti. The Tafel relations reveal new features that can be associated with the partial breakdown/decomposition of the passive layers, H absorption, and the onset of Ti hydride formation.
Date de publication	2001
Dans	Langmuir 17, nº 10 (2001) : 3051–3060.
Langue	anglais
Publications évaluées par des pairs	Oui
Publication du CNRC	Cette publication n’est pas du CNRC Ce sont des publications qui ont été rédigées par un auteur du CNRC, mais avant que celui-ci soit employé du CNRC.
Numéro NPARC	21272567
Exporter la notice	Exporter en format RIS
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Identificateur de l’enregistrement	a282ef0f-c5fa-42ff-88aa-16b8765b3212
Enregistrement créé	2014-12-02
Enregistrement modifié	2020-03-27

Date de modification :: 2024-04-19